So the funny thing about the metal bridge incident was...
If a Player was in that position and asked "Is there a tree nearby" everyone would praise them for thinking outside the box when they cut it down to use as a replacement bridge.

The problem with a DMPC in a meta sense is that it forces players to witness The Hand of God as it warps reality for the Players' convenience .

So, during my Uni years we actually had a kinda good DMPC

5 players + 1 DM in a heavily homebrewed campaign. We played mainly for the roleplaying and shenanigans, so we took combat less serious. Rule were more like guidelines.

The DMPC was a human ghost, so his interactions with loot, combat and other physical stuff was limited to non existent. The Ghost had hard times staying manifest sometimes and would hide in his anchor, an old pocket watch. That watch was a reason for a lot of laughs, getting tossed around some

The Ghost was part of the setting (necromancy everywhere), but as the ghost was more like a happy joker, he would not give every secrets away always.

To make this short, the DMPC ghost was not omnipresent, didnt tell us all secrets and didnt limit engagements. It became more of a funny occurance whenever the Ghost came up, but as not all of his appearances were important he was more like a random enjoyable addition

My group had a DMPC, but we as players took turns playing her character. The DM did the roleplay.

I like using DMPCs to supplement the actions of the party. If they're lacking a tank, they'll get a guy who can absorb hits but is lacking  in offense. That kind of thing.

My party's favorite dmpc that i introduced was a traveling cleric of a diety of roads when they really needed a guide through the region and someone familiar with the local orc tribes and such. Cleric shows up after a session or two of them struggling, the characters and him hit it off, he offers to accompany them for a time so that they don't get too lost until the party's ranger is more familiar with the region and the party itself is better acquainted with the locals. I played him as a mildly senile old man who would occasionally get distracted with reminiscing about the old days while dropping relevant facts about whatever situation they were in.

It got to the point that a couple of the more sharp players realised he was referencing events that happened long enough ago that it'd be impossible for him to have been there, or that he'd occasionally go "oh old chief so and so of the nearby dwarf hold, i had the pleasure of attending his coronation, and was saddened to hear about his passing a few years ago, but i shouldn't be surprised as he had a long life". Was really funny seeing them wonder that whether they were traveling with a mildly kooky god in disguise or a dude that just likes to make up stories.

Never really gave them a straight answer

0:12 my personal favorite, an invisible wall with floating text. That says you cannot go this way right now.

Maybe we're weird, but we tend to always use DMPC, mostly becuase our group is small.  Our group is my wife, one or two other friends (depending) and myself.  I think it's important for a DMPC to not be a "cool" DM insert, but someone to fill the gap for a party so the party isn't railroaded into playing character types they don't want to.  Also, we usually play L5R or WoD and our characters tend to be connected in some way and the DMPC is close to/related to a player.  Not the "you all meet at the tavern" trope.  This is all agreed to beforehand by all players and it integrates well.  For example on an L5R campaign a friend played a shugenja and they really needed a yojimbo.  The other players had something else in mind, so the DM created a bushi character who was assigned as second to the shugenja.  Again it's important all players are down with the DMPC and it works well with the party.

My only time playing with a DMPC was positive.

The party consisted of me (Dwarf Barbarian), my DM (Tiefling Bard), and the DM's wife (Drow Druid). A few months later, we had two more players join (a Human Warlock and a Half-Elf Rogue).

The module was the Curse of Strahd, and our DM made it clear from session 0 that his PC would not be making any narrative decisions and that we would all receive cool loot that fit our characters. Also, we all had a fair chance at dying (his bard nearly died three or four times).

It was the best D&D campaign I've ever been a part of, and it's the only one that I ever got to play all of the way through.

That being said, I'm aware that my example is an exception rather than the rule.

A good DMPC would be a Guide that cant fight but is there to help giving directions/hints for story progress after being Paid, a hired Mercenary that can be fired at any time or some Pet/Creature that the Players found and took in but nothing more.

Was introduced to D&D last year by my friend, and as we were short on players, he used a DMPC to ensure that another friend and I would have enough players to have a decent game.

His character never took the limelight and acted more like a video game A.I. companion who gave us advice when we got stuck and only really chimed in with boss fights newbies like us weren't prepared for.

He only ever brings out the character when we're short on players or to help ease newer players into the game. And every time, the PCs take centre stage more as he focused on DMing while his characters were there just in case.

I ran a DMPC for a while. Just made a character sheet for the goblin the party took with them. He only had loot they wanted to give him, and as a regular ass goblin, he had very little knowledge of the wider world and plot. He rolled around, had some moral character development, then got mind controlled by the BBEG--they don't know it yet, but he is definitely gonna appear as a thrall in the end game.

I only had a DM PC for 2 sessions in the first campaign with my brothers. She was basically the guild assigned babysitter and observer for the final exam. My plan was to give them a quest to complete and then they should get lost in the fog and get to barovia. So they fight the monster at the end of the dungeon almost die and need to be saved by the high level cleric. She kills the monster easy peasy. Leaving a big impression on my brothers. Next the know they are lost in the fog end up in barovia and don't realize for 2 hours that their supervisor is gone. It will be so much fun when they realize that Stradt has a new underling

We had a circumstantial DMPC for our Descent into Avernus game. We were about to have a new player join our group who never played before, so our DM made a Human Fighter for them, something with an easy skill floor to get a grasp of things. He managed to roll really good stats and was low key kind of proud of the character.

The player ended up not joining and the DM was kinda bummed this high Stat character wasn't going to be a thing. We told him to just have them as a background character. Never got in the way, never steered the story, rarely spoke. It was a pleasurable experience, thankfully.

8:00 up to this point you could have a twist where the DMPC was actually a minion luring the party to a trap.  Sure it still would have been a shitty journey but at least the destination would be more fun.

If the DM is nervous and doesn't know if their players are going to get it, I can cut them some slack, but to do it every time and to the point of overshadowing the party and with a voice the players hate hearing, yeah, screw that guy.

I occasionally run Dmpc's usually because party adopts a character or go looking for someone to "fill a slot" as a DM who makes loot specifically for the party loot is never really an issue, I never run them as knowing things but instead have less knowledge or the same as the party, one that my players still love was a goblin artificer raised by dwarves who joined the party to have them test her new inventions, party got lots of homebrew loot and a battle smith to help keep the party from dying

When my group first started, they lacked a spellcaster & healer; so to fulfill the part, I made a poll in the group chat.  When they rejected the idea, I was happy to oblige even given that I would be quite limited in my abilities to ensure survival.

So, I actually had my PC from a campaign I played in be a DMPC in the starting campaign for the group I DM'd for. The story behind that was that everyone in the party was new to D&D so I used my old PC to sorta show them how the game is played. The way I did it was very similar to a tutorial in some games. However the party had to fight my character. I held back a lot of the blows as at the time as a newer DM I didn't know how to convert a 15th lvl Rogue Monk multiclass into a monster CR sheet but ultimately I used him to teach the basic concepts of combat and roleplay and then he became their quest giver through the adventurer's guild they joined.

After the initial "How to Play D&D" the party loved my campaign which was essentially Tomb of Annihilation but my own twists into it. I'll probably have to write a story about it at some point.

My campaign had a DMPC that mainly just acted as extra muscle to help us fight through the strongest and final concentration of the zombie fungus horde we were dealing with. He never hogged the spotlight, let us do our own thing, and stayed behind when we went to defeat the horde at its source.

I once played with a group where we would take turns to DM. The campaign was more like "monster of the week" TV series than a over arcing story. This meant everyone had a DMPC. It was a cluster fluc. Some DMs could distance themselves from their Character when DMing, but most could not.

Any DM who wants to join the RP should look into the sidekick system from Tasha’s. Our DM did that after saying she missed the RP and it worked out very well.